Field of the Invention
The present invention relates to structures and methods for reliably generating a desired spray pattern, and, more particularly, to a showerhead that distributes water from a large showerhead front surface area. Showerheads of this type are sometimes referred to as “rain showers” or “rain can” showerheads.
Discussion of the Prior Art
A shower head is typically a perforated nozzle that generates a plurality of water jets and distributes sprayed water over a large solid angle. In water conserving designs, less water is used to shower or wet a given area. Low flow shower heads can use water more efficiently by aerating the water stream. Some shower heads can be adjusted to spray different patterns of water. Hard water may result in calcium and magnesium deposits clogging the head, reducing the flow and changing the spray pattern. Persons of skill in the art will appreciate that these design issues and many others are described in U.S. Pat. No. 7,740,186 and the prior art cited therein.
Rain can style showerheads (e.g., shown in FIG. 1A) have become increasingly popular because they provide the user with a rain-shower like pattern of spray, drenching the user's entire body with just enough pressure to make it mildly invigorating. The desired sensation for user has been described as a “natural rainfall experience” where the shower head creates a gentle, drenching rainfall-like full-body spray coverage from an array of nozzles or fluid jets originating from relatively a large showerhead front surface area.
Rain can shower heads are traditionally mounted upon a long (e.g., 13-inch) gooseneck shower arm to provide an above-the-head position, but can also be configured for use on a traditional showerhead supporting pipe nipple projecting from an elevated position on a wall. A rain-can shower head is typically larger than an ordinary shower head and may have a six-inch-diameter face with forty (40) or more spray channels, in an effort to provide the full-body drenching spray which simulates rainfall. The effect desired can be characterized as a relatively uniform spray originating from a larger surface area than is provided by a typical showerhead.
Getting a uniform pattern of spray is not easy, though. Stationary spray heads with fixed jets are the simplest of all spray heads, consisting essentially of a water chamber or manifold and one or more jets directed to produce a constant pattern. Stationary spray heads with adjustable jets are typically of a similar construction, except that it is possible to make some adjustment of the jet opening size and/or the number of jets utilized. However, these types of jets provide a straight often piercing directed flow of water. These stationary spray heads cause water to flow through apertures and continuously contact essentially the same points on a user's body. Therefore, the user feels a stream of water continuously on the same area and, particularly at high pressures or flow rates, the user may sense that the water is drilling into the body. Rain can spray heads represent an effort to reduce this undesirable feeling, by enlarging the area emitting the sprays, but each jet of water, when emitted from a static nozzle, still drills into one spot. This is why makers of rain can style showerheads wish they could provide better nozzles in their products.
Generally speaking, fluidic oscillators are known in the prior art for providing a wide range of liquid spray patterns by cyclically deflecting a liquid jet. Examples of fluidic oscillators may be found in many patents, including U.S. Pat. No. 3,185,166 (Horton & Bowles), U.S. Pat. No. 3,563,462 (Bauer), U.S. Pat. No. 4,052,002 (Stouffer & Bray), U.S. Pat. No. 4,151,955 (Stouffer), U.S. Pat. No. 4,157,161 (Bauer), U.S. Pat. No. 4,231,519 (Stouffer), which was reissued as RE 33,158, U.S. Pat. No. 4,508,267 (Stouffer), U.S. Pat. No. 5,035,361 (Stouffer), U.S. Pat. No. 5,213,269 (Srinath), U.S. Pat. No. 5,971,301 (Stouffer), U.S. Pat. No. 6,186,409 (Srinath) and U.S. Pat. No. 6,253,782 (Raghu), which are summarized below.
The operation of fluidic oscillators is usually characterized by the cyclic deflection of a fluid jet without the use of mechanical moving parts. Consequently, an advantage of fluidic oscillators is that they are not subject to the wear and tear which adversely affects the reliability and operation of pneumatic oscillators and reciprocating nozzles. The fluidic oscillators described in U.S. Pat. No. 3,185,166 (Horton & Bowles) are characterized by the use of boundary layer attachment (i.e., the “Coanda effect,” so named for Henri Coanda, the first to explain the tendency for a jet issuing from an orifice to deflect from its normal path (so as to attach to a nearby sidewall) and the use of downstream feedback passages which serve to cause the jet issuing from a power nozzle to oscillate between right and left side exit ports.
At the risk of boring those having skill in this rather specialized art, a substantive background will be provided here. It is understood that the three-dimensional character of the flow from such fluidics can take a variety of forms depending upon the three-dimensional shape of the fluidic. For example, oscillators described in U.S. Pat. No. 4,052,002 (Stouffer & Bray) are characterized by the selection of the dimensions of the fluidic such that no ambient fluid or primary jet fluid is ingested back into the fluidic's interaction region, which yields a relatively uniform spray pattern made up of droplets of more uniform size. The absence of inflow or ingestion from outlet region is achieved by creating a static pressure at the upstream end of interaction region which is higher than the static pressure in outlet region. This pressure difference is created by a combination of factors, including: (a) the width T of the exhaust throat is only slightly wider than power nozzle so that the egressing power jet fully seals the interaction region from outlet region; and (b) the length D of the interaction region from the power nozzle to throat, which length is significantly shorter than in prior ‘fluid ingesting’ oscillators. It should be noted that the width X of control passages is smaller than the power nozzle. If the width of power nozzle at its narrowest point is W, then the following relationships were found to be suitable, although not necessarily exclusive, for operation in the manner described: T=1.1−2.5 W and D=4−9 W, with the ratios of these dimensions also being found to control the fan angle over which the fluid is sprayed. By adding a divider in this fluidic's outlet region, it becomes what can be referred to as two-outlet oscillator of the type that might be used in a windshield washer system. See, for example, U.S. Pat. No. 4,157,161 to Bauer.
The fluidic oscillators described in U.S. Pat. No. 4,231,519 (Stouffer, reissued as U.S. Pat. No. RE 33,158), are also unique in that they employ yet another fluid flow phenomena to yield an oscillating fluid output. The oscillators of U.S. Pat. No. 4,231,519 are characterized by their utilization of the phenomena of vortex generation, within an expansion chamber prior to the fluidic's throat, as a means for dispersing fluid. It comprises a jet inlet that empties into an expansion chamber which has an outlet throat at its downstream end. It also has an interconnection passage that allows fluid to flow from one side to the other of the areas surrounding the jet's inlet into its expansion chamber. The general nature of the flow in such fluidics is that vortices are seen to be formed near the throat. As the vortices grow in size they cause the centerline of the fluid flowing through the expansion chamber to be deflected to one side or the other such that the fan angle of the jet issuing from the throat ranges from approximately +45 degrees to −45 degrees. The result of these flow oscillations is a complicated spray pattern, which at a given instant takes a sinusoidal form (similar to that shown in FIG. 6(e) in commonly owned U.S. Pat. No. 6,805,164).
The fluidic oscillators disclosed in U.S. Pat. No. 5,213,269 (Srinath) and U.S. Pat. No. 5,971,301 (Stouffer) are referred to as “box oscillators” having interconnects which serve to help control the oscillating dynamics of the flow that exits from the fluidic's throat. For example, the effect of these interconnects, assuming that they are appropriately dimensioned relative to the other geometry of the fluidic, is generally seen to be about a doubling of the fan angle of the fluid exiting from the fluidic's throat. FIG. 8(a) from U.S. Pat. No. 5,213,269 shows an embodiment in which the interconnect takes the form of passage that connects points on opposite side of the fluid's throat. FIG. 8(b) from U.S. Pat. No. 5,971,301 shows an embodiment in which the interconnect takes the form of a slot in the bottom wall of the fluidic's interaction region.
U.S. Pat. No. 6,253,782 (Raghu) discloses a fluidic oscillator of the type that provides a shaped interaction region having two entering power nozzles and a single throat through which the resulting fluid flow exits the fluidic oscillator. See FIGS. 9(a)-(b). The jets from the power nozzles are situated so that they interact to form various vortices which continually change their positions and strengths so as to produce a sweeping action of the fluid jet that exits the throat of the fluidic. In a preferred embodiment, the interaction region has a mushroom or dome-shaped outer wall in which are situated the power nozzles.
U.S. Pat. No. 6,186,409 (Srinath) discloses a fluidic oscillator which has two power jets entering a fluid interaction region from the opposite sides of its longitudinal centerline. The jets are fed from the same fluid source, and are unique because they employ a filter between the jet source and the upstream power nozzles to remove any possible contaminants in the fluid.
The instant applicant has patented shower head and personal spray devices with oscillating fluid jets, but has never applied fluidic technology to a rain can style showerhead. As noted above, this application is commonly owned with U.S. Pat. Nos. 4,122,845 and 7,111,800, the entire disclosures of which are also incorporated herein by reference. Fluidic oscillators, as described in these patents and other patent applications to this applicant, have no internal moving parts, and yet are capable of generating an oscillating spray of droplets which are much more like rainfall than the standard showerhead's water-drilling static jets.
Unfortunately, it is not a trivial matter to replace nozzles generating static jets with fluidic oscillators. In many liquid spray applications, like the rain can showerhead assembly, a plurality of nozzles fed via a bowl-shaped showerhead water chamber or manifold have a central flow inlet which may be configured with a pivoting ball joint so that the shower head assembly can be aimed. In such cases, because of the nature of the inlet, the flow inside the manifold becomes very turbulent. Fluidic inserts are sensitive to turbulence and a traditional nozzle assembly or shower head incorporating a traditional fluidic circuit will not spray or fan as intended, because turbulent inlet or manifold flow disrupts the operation of traditional fluidic oscillators.
There is a need, therefore, for a reliable, inexpensive and unobtrusive system and method for improving the operational characteristics of devices including fluid manifolds or other fluid conveying structures that are prone to generating turbulent inlet flow.